221 research outputs found
New measurement of DeltaG/G at COMPASS
One of the main goals of the COMPASS experiment at CERN is the determination
of the gluon polarisation in the nucleon, DeltaG/G. It is extracted from the
spin asymmetry in the scattering of a polarized 160 GeV muon beam on a
polarized LiD target, by selecting photon-gluon fusion events. These events are
tagged by the production of open charm or high pT hadron pairs. We present the
results obtained for DeltaG/G(x) in both channels. For the first time,
preliminary results of 2004 data in the high pT channel are also shown.Comment: 4 pages, 5 figures, Moriond-QCD 2006 conference proceeding
Determination of Polarized PDFs from a QCD Analysis of Inclusive and Semi-inclusive Deep Inelastic Scattering Data
A new combined next to leading order QCD analysis of the polarized inclusive
and semi-inclusive deep inelastic lepton-hadron scattering (DIS) data is
presented. In contrast to previous combined analyses, the terms
(kinematic - target mass corrections, and dynamic - higher twist corrections)
in the expression for the nucleon spin structure function are taken into
account. The new COMPASS data are included in the analysis. The impact of the
semi-inclusive data on the polarized parton densities (PDFs) and on the higher
twist corrections is discussed. The new results for the PDFs are compared to
our (Leader, Sidorov, Stamenov) LSS'06 PDFs, obtained from the fit to the
inclusive DIS data alone, and to those obtained from the de Florian, Sassot,
Stratmann, and Vogelsang global analysis.Comment: 11 pages, 8 figures, a version to be published in Phys. Rev.
Analysis of the electron component of EAS at observational level 700 g x cm(-2) with a scale breaking interaction model and gammaisation hypothesis
Scale breaking model and gammaisation processes for high energies give a correct description of the longitudinal development of extensive air showers (E.A.S.). From the analysis of phenomenological characteristics of E.A.S. at Tien-Shan experiment, it follows that for energies near 10 to the 6 GeV the secondary particle multiplicity increases with energy faster than is predicted by the accepted scale breaking model
Polarization state of atmospheric Cerenkov events-guidance from simulation studies
We have been systematically carrying out experimental and simulation studies of the polarization properties of atmospheric ˇCerenkov events (ACE) produced by very high energy (VHE) and ultrahigh energy (UHE) γ-ray and cosmic
ray proton progenitors. We present here an interim report on the work, based on some recent simulation investigations
Experimental Investigation of the Nature of the Knee in the Primary Cosmic Ray Energy Spectrum with the GAMMA experiment
We present preliminary results obtained by a novel difference method for the
study of the nature of the knee in the energy spectrum of the primary cosmic
radiation. We have applied this method to data from the GAMMA experiment in
Armenia. The analysis provides evidence for the possible existence of a nearby
source of primary cosmic rays in the Southern hemisphere.Comment: 17 pages, 5 figure
New pixelized Micromegas detector with low discharge rate for the COMPASS experiment
New Micromegas (Micro-mesh gaseous detectors) are being developed in view of
the future physics projects planned by the COMPASS collaboration at CERN.
Several major upgrades compared to present detectors are being studied:
detectors standing five times higher luminosity with hadron beams, detection of
beam particles (flux up to a few hundred of kHz/mm^{2}, 10 times larger than
for the present Micromegas detectors) with pixelized read-out in the central
part, light and integrated electronics, and improved robustness. Two solutions
of reduction of discharge impact have been studied, with Micromegas detectors
using resistive layers and using an additional GEM foil. Performance of such
detectors has also been measured. A large size prototypes with nominal active
area and pixelized read-out has been produced and installed at COMPASS in 2010.
In 2011 prototypes featuring an additional GEM foil, as well as an resistive
prototype, are installed at COMPASS and preliminary results from those
detectors presented very good performance. We present here the project and
report on its status, in particular the performance of large size prototypes
with an additional GEM foil.Comment: 11 pages, 5 figures, proceedings to the Micro-Pattern Gaseous
Detectors conference (MPGD2011), 29-31 August 2011, Kobe, Japa
A new approach to calculate the gluon polarization
We derive the Leading-Order master equation to extract the polarized gluon
distribution G(x;Q^2) = x \deltag(x;Q^2) from polarized proton structure
function, g1p(x;Q^2). By using a Laplace-transform technique, we solve the
master equation and derive the polarized gluon distribution inside the proton.
The test of accuracy which are based on our calculations with two different
methods confirms that we achieve to the correct solution for the polarized
gluon distribution. We show that accurate experimental knowledge of g1p(x;Q^2)
in a region of Bjorken x and Q^2, is all that is needed to determine the
polarized gluon distribution in that region. Therefore, to determine the gluon
polarization \deltag /g,we only need to have accurate experimental data on
un-polarized and polarized structure functions (F2p (x;Q^2) and g1p(x;Q^2)).Comment: 12 pages, 5 figure
Characteristics of air showers created by extremely high energy gamma-rays
The technique of adjoint cascade equations has been applied to calculate the
properties of extremely high energy gamma-rays in the energy range 10^18--10^22
eV with taking into account the LPM effect and interactions of gamma-rays with
the geomagnetic field. Such characteristics are analysed as the electron and
muon contents at the observation level, the electron cascade curves, the
lateral distribution functions of photoproduced muons.Comment: 36 pages, 19 figures, submitted to J.Phys.G: Nucl.Part.Phy
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